During reconstitution of the olfactory epithelium (OE), after injury, the spatially restricted pattern of odorant receptor (OR) expression is restored with remarkable fidelity. The population of globose basal cells (GBC) is damaged to a variable extent after direct injury to the OE, so it is unlikely that the position of the GBCs provides the memory for spatial position that drives OR expression. We hypothesize, therefore, that the cellular basis for "memory" of epithelial space resides in the extra-epithelial component of the mucosa. We will test that hypothesis by transplanting GBCs from one region of the OE into a different part and examining the ORs expressed by descendent neurons during reconstitution after lesion. In addition, we will examine RA as a potential candidate cue for providing spatial memory to the GBCs, by manipulating the concentration of RA in the OE and assaying for OR expression patterns. Finally, we will examine the potential involvement of the homeobox-containing transcription factor, msx-1, as an intermediary in the actions of RA.